Process of concentration of solutes



Oct. 4, 1966 A. F. REID PROCESS OF CONCENTRATION OF ASOLUTES Original Filed March '7, 1958 AEL-; N m, ln|||11 mi- A||| NG Q W il-: W v. u u n n n t :IV --.-v S 1- .Y m w Iv llv l||1V NQ n s M |-lxmlnm.|\xlmlr,\ljl n u n u um, n M ||.l, l l l l lx lxll \L Q m N INVENTOR. L L P/v /1' /QE/D BY c/*j United States Patent O 3,276,997 PROCESS OF CONCENTRATION OF SOLUTES Allen F. Reid, 3145 Spur Trail, Dallas, Tex. Original application Mar. 7, .1958, Ser. No. 719,905, now Patent No. 3,097,076, dated July 9, 1963. Divided and this application May 21, 1963, Ser. No. 281,943

Claims. (Cl. 210-23) This is a division of my copending application Serial No. 719,905, led March 7, 1958, for Process of Concentration of Solutes, now Patent` No. 3,097,076, issued on July 9, 1963.

This invention relates to the relative concentration of one or more of the constituents of a liquid composition such as a solution.

The object of the invention is to provide a process subjecting the solution to a seriesof treatments in order to increase the proportionateamount of one or more constit-uents of the solution in part of the solution, while at the same time decreasing their concentration in the remaining portion of the solution.

It is a further object of the invention to provide a method employing a series of operations with a recycling and reconditioning of process materials to produce the desired products in an energy-conserving and economic manner.

A special object is the production of industrial, agricultural or domestic household water from sea or brackish water where economy of production is intimately tied to the energy requirements.

In the following description a preferred embodiment is set forth in connection with a drawing showing a ilow diagram of a separation process.

In general, the mechanism of this process consists of the treating of a portion of the solution at hand, the introduction of this portion of the solution into a concentration varying cell wherein the starting strength of the original solute is either increased or decreased by the action of the cell followed bythe removal of the solutiton from the cell and the treatment of the solution in order to reestablish the original conditions for the process.

Another portion of the solution is left untreated, is passed into a cell wherein the concentration of the solute is changed in the direction opposite to that of the treated solution, is removed from the cell, and is treated to reestablish the original conditions for the process.

As a result of these operations, a solution with an intermediate concentration of solute has been processed to yield one portion of a more highly concentrated solution and one portion of a depleted solution. For simplicity the terms solute and solvent are intended to include generally the constituents of a colloidal suspension as well as those of a true solution. Where further concentration or depletion is desired beyond any stage, the products of the concentration procedure described may be further treated by the same process with recycling methods known in engineering practice. One of these recycling methods is the placing of each separationV stage contiguous to the next stage with the same type of countercurrent operation as is used in a rectifying system. Another method is a recycling arrangement such as that described in my U.S. Patent 2,772,953, dated December 4, 1956.

One method for obtaining a change of concentration of the solute in a solution as disclosed -by this inventiton is the application of the Donnan elect in the concentration cell. The ilow of ions across a semipermeable rnernbrane which is permeable to those ions is affected by the concentration of ions which will not freely penetrate the membrane. This phenomenon is called the Donnan effect.

An example of the operation of this efrect is that involving a large molecule NaR which in solution exists in 3,276,997 Patented Oct. 4, 1966 a dissociated state Na+ plus R+. If a semipermeable membrane is chosen which prevents the passage of R- and NaR but allows the passage of Na+ and Cl, and if a system is set up with a solution of NaR on one side of the membrane and water on the other side, only a very small amount of Na+ could diffuse through the membrane before the huge electrostatic gradient developed at the membrane prevented further transfer. On the other hand, a solute NaCl would diffuse readily across the membrane because it is present as Na+ and Cl, both of which can diffuse across the membrane and thus may 'be transported in pairs without building up a large electrostatic gradient across the membrane. Ifr both NaR and NaCl are placed on one side of the membrane, Na+ and Clwould tend to diifuse across the membrane together with the object of establishing equal concentrations of sodium ions and chloride ions on both sides of the membrane. However, since an equal nu-mber of sodium ions and chloride ions tend to diffuse across the membrane, at the time the Clconcentration has become equal on both sides of the membrane, the Na+ ion concentration still remains higher on the side with the R+. On the other hand, if the Na+ were to continue to diffuse to the other side to equal concentration on lboth sides of the membrane, then Clions passing with them Would correspondingly reduce the Clconcentration to be lower on the side of the R".

This is resolved by compromise: a steady state with a somewhat greater Na+ concentration is established on the R side with the tendency to diluse toward the other side, and a slightly greater concentration of C1 is established on the side opposite the R- tending to diff-use toward the R- side. The thermodynamic relationships are approximately that [Na+]1 [Cl]1=[Na+]2 [Cl-h where the subscripts denote the sides of the membrane. A similar situation exists where the non-transferable ion is a cation, where the ions involved are multivalent, where mixtures of compounds are present and where the ions are in colloidal suspension.

In an application of the Donnan effect in this invention, if we designate the salt Whose concentration We wish to change in the solution by BX which ionizes to B+ and X- and if we designate the foreign solute to be added by Z, the operation of the method in this example depends on Z having Ithese properties:

(l) Z is ioniza'ble with one ion, either the anion or the cation, common to one of the ions of the salt to be concentrated (B+ or X).

(2) The other ion of Z not common to an ion of said BX, is not diffusible or only slowly dilusible 4through a membrane permeable to BX.

(3) Z is soluble in a volatile liquid L (which is not miscible with the original solvent) to the extent that Z may be extracted by L from the solvent.

i The process of operation of a single stage would then be as follows:

(l) Placing the solution of BX on both sides of a semipermeable membrane and adding Z to one side. By the Donnan el-lect the concentration of the BX on the opposite `side is increased, that on the side with Z is decreased.

(2) Removing the Z-con-taining solution from the system and extracting the Z with L. This leaves one part Vin- `creased in BX concentration and one part decreased in BX concentration.

(3) Concentrating Z in L by distilling off some of the L. This concentrated solution of Z in L can then furnish Z to more solution by extraction.

The following example serves to illustrate the method:

Equal volumes of two aqueous solutions, A and B, were placed on opposing sides of a cellulose membrane permeable to water and NaCl but only very slowly permeable to stearyl dimethyl benzyl ammonium ion (Y+) 3 and left for 30 minutes at 25 C. Originally solution A was 0.0240 molal to NaCl and 0.085 molal to YCl; and solution B was 0.0240 molal to NaCl with no YCl. At the end of the 30 minute interval, solution A was 0.0166 molal -to NaCl and 0.083 molal -to YCl; and solution B was 0.0314 molal to NaCl and 0.0017 molal to YCl. The

product solutions A and B were extracted with CH2C12, decreasing their YCl concentration to insignificant concentrations. Part of the CH2C12 was evaporated, thereby concentrating ZCl in the unevaporated portion to the point furnishing a signiiicant concentration of ZCl to a water solution upon extraction by it.

Another example under somewhat dilferent conditions was an operation at 78 C. Solutions C and D were placed on opposing sides of a membrane permeable to NaCl but not to di-isobutyl cresoxy ethoxy ethyl dimethyl benzyl ammonium ion (Wi). Solution C was 0.60 molal to NaCl and 0.316 molal yto WC1; and solution D 'was 0.60 molal to NaCl with no WC1. After 30 minutes the procedure was discontinued and the WC1 was extracted from the resulting C and D solutions with CHC13. The product C solution was 0.50 molal to N-aCl and the product D solution was 0.70 molal to NaCl. VAn alternative method of removal of the WC1 from solution was demonstrated by taking a solution identical with solution C and cooling to 8 C. Practically all the WC1 separated out leaving a supernatant solution with `a ZCl concentration less than 0.0005 molal. When desired, the separated WC1 may be redissolved in another solution at temperatures at` which it is soluble. This variation of means of removal of an added solute may be used when appropriate in any method set forth in which treatment of the solution is by addition of 4another solute. Another example illustrates the case where the common ion is the cation. Equal volumes of solutions E and F were placed on opposing sides of a cellulose membrane permeable to NaCl 'but only very slowly permeable to dioctyl sulfosuccinate ion (V*) for one hour at 25 C. The original solution E was 0.0240 molal to NaCl and 0.0293 molal to NaV; and solution F was 0.02.40 molal to NaCl with no NaV. At the end of the hour, E was 0.0187 molal to NaCl and `0.0283 molal to NaV; and F was 0.0293 molal to NaC-l and 0.0010 molal to NaV. The NaV was extracted from these solutions with ChCl3.

In these three samples it is seen that a solution with an intermediate concentration of solute has been processed to yield one portion of a more highly concentrated solution and one portion of a depleted solution.

As an example of -the combining of several stages of separation, a system was set up to vary the concentration of NaCl with dioctyl sodium sulfosuccinate (NaV) as the added solute. A 208 centimeter long polyethylene tube, 9.5 millimeters in diameter, was divided into two compartments by ya cellulose membrane which ran the length of the tube. A solution G Was introduced at one end of the tube'on one side of the membrane, and a solution H was introduced at the other end of the tube on the other side of the membrane. Both solutions ran the length of the tube butin a countercurrent direction to each other, lleaving the tube at the opposite end but on the same side of t-he membrane -from which they started.V VThis system was operated for eleven hours to allow operation to be in a relatively steady state, after which production samples were taken for analysis. Before entering thisy concentration cell, solution G was 0.0240 molal to NaCl and 0.0348 molal to NaV; and solution H was 0.00240 molal to NaCl with no NaV; The product G was 0.0011 molal -to NaCl and 0.0298 molal to NaV; and the product H was 0.0274 molal to NaCl and 0.0052 molal to NaV. The total flow of G during the four-hour production run was 52.2 milli- 4liters; and the total flow of solution H was 42.5 milliliters. The operation of this series of stages of concentration and depletion may be traced by starting at the end at which G is introduced and H leaves. Solution G loses some of its NaCl through the membrane and continues on its way down `the tube. Solution H ows in the opposite direction,` continuously acquiring an increased concentration of NaCl from the G on the other side of t-he membrane, and dinally leaving .the system with a concentration of NaCl as the original concentration of NaCl in H. The `NaV may be removed from this; a small amount of the solui tion may be removed as product; and the remainder may be reintroduced into -the system as solution H. As an over-all consequence of this method of operation through 1 several concentration stages and reflux at one end, t-he original solution G is separated into two portions, one

with a higher and one with a lower concentration of NaCl.

When desired, the adaptation to a system with rellux and production at both ends can bemade using standard engineering principles.

other methods described.

Another method for obtaining a change of concentration of the solute in a solution as disclosed .by this invention is .the utilization of the .changey in solubility of a solute when another solute is introduced into the` solui When a solute is soluble in each of two solvents tion. which are found in phases communicating with each other, that solute will distribute itself in such a manner as to favor concentration in the solvent in which it isj There are many instances in which the more soluble. addition of a second solute to a solution will decrease the solubility of such a solute. Thus if a semipermeable membrane is placed to separate two portions` of a solu-` tion of a solute A, and a second solute U of .the type which decreases the solubility of A is placed in one portion of the solution, then the A will redistribute itself in the two portions by becoming less concentrated in the U`` vcontaining portion. The operation of the method in thisl example, then, depends on U having these properties:

(1) U is only slowly diifusible or not diiusible through a membrane permeable to the solutewhich is'to be concentrated.

(2) The addition to the solvent of U changes the solubility of A therein.

(3) U is soluble in a volatile liquid L (which is not miscible with the original solvent) to the extent that1U may be extracted by L from the solvent.

'Ihe processtof operation of a single stage would then be as follows:

(1) Placing the solution of A on both sides of a semipermeable membrane and adding U to one side. The

concentration of Alon :the U side` is increased or de creased While tha-t on the other side is decreased or in-` creased correspondingly.

(2) Removing the U-containing solution from the system and extracting the U with jL. This leaves one solu-` tion increased in A concentration and one decreased in A concentration.

(3) Concentrating U in L by distilling `oti isome `of the L. This concentrated solution of U in `L can then` furnish U to more water solution by extraction.`

The yfollowing example serves to illustrate the method: Equal volumes of solutions J and K were placed on opposing sides of a cellulose membrane, permeableto water but only very slowly permeable to dioctyl sodium` sulfosuecinate (NaV), for 30 minutes at 25 C. The

solvent was l,1,2,2tetrachloroethane. NaV increases the solubility of water in the solvent. The original solution I had one part rwater and 43 parts of NaV per 1000 parts by volume of solvent; and solution K had one part water per 1000 parts of solvent with no NaV. At the.

end of the SO-minute interval, solution J had 1.8 parts Water per 1000 parts of solvent, andsolution Khad 0.2 part of water per 1000 parts of solvent with no appreciable concentration changes of NaV. The NaV in I was ex- Very simil-ar engineering maybe done to unite for a concentration cell several stages of the` tracted with water decreasing its concentration in the solvent to an insignificant value.

Another example illustrates the case where the added solute decreases solubility of the original solute in a solvent:

Equal volumes of two aqueous solutions L and M were placed on opposing sides of a cellulose membrane permeable to water and NaCl but only slowly permeable to the surface active agent GPH-30, manufactured by the C. P.` Hall Company. GPH-30 is a polyethylene glycol monolaurate, is non-ionic in character, is completely water-soluble at ordinary room temperatures, and becomes insoluble as the temperature rises above 31 C. Solu- .tion L was 0.30 molal to NaCl and 20 percent GPH-30 by volume. Solution M was 0.30 molal to NaCl. The solutions were left on opposing sides of the membrane 'at 25 C. for 30minutes and then removed. There 'was no appreciable change in GPH-30 concentration in the solutions but solution L had beco'me 0.267 molal to NaCl and solution M had become 0.333 molalto NaCl. Solution L Was then heated to 60 C. At 31 C. a large portion of the U had separated out and at 60 C. had mostly coalesced and risen to the top, leaving a subnatant solution with a GPH-30 concentration of less than 0.02 percent. When desired, the separated GPH-30 may be redissolved in another solution at temperatures at which i-t is soluble. This example illustrates another variation of the means of removal of an added solute which may be used when appropriate in any method set forth in which treatment of the solution is by addition of another solute.

Another method for obtaining la change in concentration of a solute in a solution as disclosed by this invention is the utilization of selective sorption by ion exchange resins in the separation cell. An ion exchange resin will exchange ions which are sorbed to it for other ions of the same charge when it is placed in contact with a solution of these other ions. An example of this is a cation exchange resin Which has been in lsucient contact with a solution of NaCl so that it is saturated with Na+. Another solute RC1, which ionizes to R+ and Clin the solvent, is added to the solution. The ions sorbed .to the resin are in constant exchange with the ions in the solution; consequently, some of the R+ ions are sorbed by the resin which gives olf in exchange some of the Na+ lons.

Another example would be an anion exchange resin saturated with Cl in a NaCl solution. If another solute NaR, which ionizes to Na+ and R, is added to the solution, the 4resin will exchange some of its Cl for some of the solutions R+. If We designate the salt whose concentration We wish to change in the solution as BX, which ionizes to B+ and X", and if We designate the salt to be added as T, the operation of the method in this example depends on T having these properties:

(1) T is ionizable with one ion common to one of the ions of the salt to be concentra-ted (B+ or X-).v

(2) The other ion of T is exchangeable with .the other ion of BX on an ion exchange resin.

(3) T is soluble in a volatile liquid L (which isnot miscible with the original solvent) to the extent that T may be extracted from .the original solvent.

The method of operation of a single stage would then be as follows:

(1) A bed of resin is conditioned to the solution BX.

(2) T is added to a portion of the BX solution to be concentrated in BX :and the solution is placed in contact with the resin. There is then an increase in concentration of BX in this solution with a corresponding ydecrease in concentration of T.

(3) The solutionis removed from the resin.

(4) If further concentration is desired, that portion enriched in BX can be advanced to the next stage without extraction of the T. If no further concentration is desired, the T may be extracted with L.

(5) Another por-tion of the solution to which T has not been added is placed in contact with the resin. It

becomes less concentrated in BX and acquires T from the resin.

(6) This solution is removed from the resin.

(7) T is extracted with L from the solution depleted in BX, which leaves a solution that can be used directly, or which can be sent to a succeeding stage if further deplet-ion is desired.

(8) The process continues with the .alternate treating of the resin with a solution enriched in T and a solution Without T.

(9) T is concentrated in L -by distilling oi some of L. This concentrated solution of T in L can then furnish T to more water solution by extraction.

The following example lserves to illustrate the method:

17.5 cc. of Dowex 50X4, a cation exchange resin manufactured by The Dow Chemical Company, were placed in a stainless steel screen basket which was alternately dipped into solutions N and P. Solution N was an aqueous solution 0.050 molal to NaCl and 0.050 m-olal to di-isobutyl cresoxy ethoxy ethyl dimethyl benzyl am? monium chloride (WC1). Solution P was 0.050 molal to NaCl with no WC1. After extensive conditioning in this manner, a series of 20 minute dips of the basket was made at 25 C. into 120 cc. batches of fresh solutions of N and P alternately. During a typical dip into P solution the resin gained 0.063 millimole of Na+ 'releasing at the same time 0.063 millimole of W+ to the solution. On the succeeding dip into solution N, the'resin lost 0.063 millimole Na+ to the solution and gained 0.063 millimole W+ from the solution. In all of thesealternate dips the resin exchanged W+ Vfor Na+ when dipped into solution P, and exchanged Na+ for W+ when dipped into solution N. The W+ was removed in the form of WC1 from the resultant solutions-by extraction with CHC13 thereby leaving one portion of a solution more concentrated in NaCl and one portion less-concentrated in NaCl than the original-NaCl solution of intermediate concentration. v

A11 alternative method of removal of the WC1 from solution was demonstrated by placing -a solution identical-with solution N in contact with linelydivided activated charcoal. Practically all the WCl was sorbed to the charcoal leaving a solution with a WC1 concentration less than 0.00015 molal. The WC1 may'be recovered from the sorber by conventional methods Vsuch as leaching withv methanol or chloroform, Awith subsequent distilla` tion of this solvent. This variation of means of removal of yan added solute may be used when appropriate in any method set forth in which treatment of the solution is by the addition of another solute. i Y

A method similar to the use of ion exchange resins in the separation cell is the use of other solid sorbers in the separation cell, a significant difference being that it is not necessary that either the solute to be variedl or'the added solute be ionizable.V

The following example serves to illustrate the method:

Powdered fullers earth which had been preconditioned by immersion in solutions of trichloroacetic ac-id and GPH-50A was alternately placed into about 20 times its weight of solutions Q and R. Solution Q was an .aqueous solution 0.044 molal to trichloroacetic acid and l0 percent GPH-30. Solution Rl was 0.044 molal -to trichloroacetic acid with no GPH-30. The contacts were made for periods of 20 minutes at 20 C.,vafter which the fullers earth was removed from the solution land placed in the alternate solution. vDuring each dip in solution R the fullers earth would sorb some trichloroacetic acid and would release to the solution some CPH- 30. During the contact with solution Q the fullers earth would sorb GPH-30 and release to the solution some trichloroacetic acid. In such a complete cycle one portion of solution would be depleted and one wouldbe concentrated in trichloroacetic acidA with no net change in theV fullers earth. Whendesired to remove the GPH-30 from the solutions, they could be heated to 60 C. at

raar/earn' 7 which temperature the CPH-30 would separate out and coalesce for easy removal.

Another method for obtaining a change of concentration of the solution in a solution as disclosed by this invention is the utilization of the change in chemical po# tential which is generally reflected by a change in solubility of a solute with a change in temperature. As stated before, when a solute is solubile in each of two solutes which are found in phases communicating with each other, that solute will distribute itself in such a manner as to favor concentration in the solvent in which -it is more soluble. Thus, if a member or other means of suitable division is placed between two portions of a solution of a solute which has a solubility change with temperature, rthen the solute will redistribute itself in the two portions if the temperatures of the -two portions are dilerent from each other. Redistribution will occur in such a manner as to favor concentration of the sol-ute in the solvent at the temperature at which it is more soluble.

The process of operation of a single stage would then be `as follows: n

(1) Placing portions of the solution on both sides of a membrane permeable to the solute and heating the solution on one side. The concentration of the solute on the heated side is increased and that on the cooler side is de-V creased, if the solubility of the solute increases with temperature; and the concentration of the solute on the heated side is decreased and that on the cooler side is increased, if the solubility of the solute decreases with temperature increase.

(2) Removing any heat not useful in further concentration steps and using it to heat other solutions in which the solute is to be concentrated or depleted.

The following example serves to illustrate the method:

Two liters of an aqueous solution 0.200 molal to CaCl2 were placed on each side of a 16 cm.2 cellulose membrane, permeable to -both water and calciumchloride. On side A the temperature was held at 20 C. On side B the temperature was held at 50 C. After a S-hour interval, the calciumchloride on side B was 9 percent higher in concentration than the calcium chloride solution on side A.

Separation between the two phases may also be accomplished by a divider yother than a membrane. As a-n example, a thin layer of foam rubber which has communicating avenues from one side to the other may be used. The temperatures used are not critical, except that the two opposing temperatures should not be chosen at which the chemical potential of the solute is the same.

An example of this modification is the following:

Two liters of an aqueous solution 0.200 molal to CaClg were placed on each side of a 16 cm.2 thin sheet of foam rubber permeable to both water and calcium chloride.

On side A the temperature was -held at 20 C. On side i B the temperature was held at 50 C. After a 3-hour interval the calcium chloride on sideY B was l percent higher in concentration than the calcium chloride solution on side A.

The lengineering of a system Yemploying one of the" methods as `an example of operation of ,the processes is' described here with reference to the drawing in which: 1 is a concentration cell; 2 and 11 are stills; 3, 4, 5,` 6, 7, 8, 9, 10 and 14 are yliquid-liquid extractors; 12, 13 and are reservoirs. BX is the solute` to be concentrated and depleted in the solvent S, shown as water in the drawing; Z is an added solute; L is a solvent for extracting Z from S, Eand T is a solvent for extracting L from S, leaving BX..

The oper-ation is as follows:

(1) The S solution to be processed, S0, enters extractor 14, enters an intermediate stage of cell 1, 4goes up to 3 becoming richer in BX as it goes, picks up Z in extractor 3, Igoes down through 1 on the other side of the membrane -becoming depleted in BX as it goes, enters extractor Y (3) Pure L from stills 2 and llextracts the last Z from S1 and Sz-res-pectively in 7 and 8. The eiiiuent L is joined at 13 by more L depleted in Z from passing through 14; this extracts Z from rthe greater concentrates in 5 Iand 6. Some of thiseiiiuent extracts the retiuxing S in 4 and is carried to 2; at 2 the Z is concentrated in L' by distillation sufficiently so that it can enrich the refluxing S appropriately in passing through 3. There may be 1 cases where it is more practical to completely distill off L at 2 and transfer the residual Z directly to the solution in which i-t is to be dissolved, thereby eliminating the` need for extractor 3.

Very similar engineering may ybe done where operation 1 of the process employs another of the methods described in their variations. For example: the substitution of ab-` sorbers or thermal separators for extractors, `the use of two alternating concentration cells instead of one coni taining ion exchange resin or solid adsorber, thereby prol viding continuous rather than intermittent flow in the 1 rest of the system, and so forth.

For the purpose of providing a clear understanding of this invention but without imposing limitation thereon, it will be described with more particular reference .to the change of concentration of sodium chloride in a .waterf e solution. Making reference to the drawing with the operation as described above, the solution to be varied, S0,

is 0.60 molal NaCl in water. For each 3 volumes of S0 supplied there is a yield of l volume of S1, 1.78 molal NaCl, and 2 volumes of S2, 0.01 molal NaCl. The added solute is Z; the extracting liquid L is CHC13; the extracting liquid T is a hydrocarbon of low volatility; the distribu-` i tion between CHC13 and water of Z is approximately 3 to 1. The concentrations, volumes and the rates of liow of the processed material from stage to stage may be determined by reference to Table- 1.

TABLE 1 Solvent Frome To- VolumeV Suppl In this operationof the method the main `energy requirements are the operation of stills 2 and 11, evaporat- 9 ing L. Using standard engineering practices, a large portion of that enery may be recovered in the subsequent condensation of the L. An advantage of this system over direct evaporation is that the total heat energy requirements for evaporation can be made lower if the latent heat of vaporization of L is less th-an that of S or if the distribution of Z between L and S effectively concentrates the Z in L so that a relatively smaller amount of L must Ibe evaporated for the same production of depleted or concentrated solutions. Since the heat of vaporization per volume of CHC13 is only about 16 percent .of the @heat of vaporization per .volume of water, and since only 1 volume of CHCI3 is distilled for each 2 volumes of S2 produced, the distillation energy requirements using this system are only about 8 percent of lche energy requirements in conventional distillation for -the production of the same amount of relatively salt-free water.

A wide range of substances may be separated, or may be concentrated, or depleted in solution by the above process. While specific examples have been illustrated, there are other systems for obtaining concentration changes for a collection of other solutes, other ion exchange resins, other solvents, other temperatures, other separators, or other methods of recycling. A range in the degree of concentration is also possible by changes in these variables when more than one solute is present in the same solution.

Principles of separation may be extended to each solute individually; it is thereby evident Ithat changes in concentration of the individual solutes may be at different rates so that the ratios of concentration of these solutes may be changed in the operation; this is tantamount to relative separation of multiple constituents of a solution.

Several methods of the process may be combined, or the methods may be combined with methods of other processes7 Iall in conformance with the steps as explained above, and it will be understood that various modifications can be made without departing from the practice of the invention as set forth in the appended claims.

I claim:

1. A process comprising a series of treatments for increasing the concentration of an ionizable lirst solute in one separated portion of a given solution while decreasing the concentration of said first solute in another portion of the said given solution, comprising the steps of treating the separated portion of the solution by adding thereto a second ionizable solute with one ion common to the rst solute to be varied, introducing said treated separated portion into a concentration cell containing an ion exchange resin which exchanges ions of charge opposite to that of the like ions of the solutes, and exchanging the ions having charges opposite to the like ions of the solutes to increase the concentration of the first solute in the treated sepa-rated portion, removing the Ithus ion exchange treated portion from the oell to form the separated first treated portion alternatingly introducing an untreated portion of the given solution to the concentration cell, exchanging ions having a charge opposite to that of the like ions of the solutes for decreasing the concentration of the rst solute and for acquiring the second ionizable solute to form a second ion exchange treated portion, removing the second ion exchange treated portion from the concentration cell to form the separated second treated portion and removing the second solute from said separated rst and second treated portions to re-establish the condition of said portions prior to the addition of said second solute except for the degree of concentration of the rst solute to be varied.

2. A process comprising a series of treatments for increasing the concentration of an ionizable first solute in one sepa-rated portion of a given solution while decreasing the concentration of said first solute in another portion of said given solution as set forth in claim 1 in which removal of the second solute is by extraction with another solvent.

' 3. A process comprising a series of treatments for in'- creasing the concentration of an ionizable lirst solute in one separated portion of a given solution while decreasing the concentration of said first solute in another portion of said given solution as set forth in claim'l in which removal of the second solute is sorption by a solid material.

4. A process comprising a series of treatments :for increasing the concentration of an ionizable first solute in one separated portion of a given solution while decreasing the concentration of said rst solute in another portion of said given solution as set forth in claim 1 in which removal of the second solute is by change in the temperature of the solution.

5. A process for increasing the concentration of a rst solute in one separated portion of a given solution while decreasing the concentration of said rst solute in another portion of said given solution comprising the steps of treating the separated portion of the solution by adding a second solute to the separated portion of said given solution to form a iirst treated portion and alternately introducing the iirst treated portion and a second untreated'portio-n into a concentration cell containing a material which reversibly sorbs the rst solute to be varied and the second solute, said first and second portions being removed from the cell before the other is introduced into the cell, and removing the second solute from said first treated portion after removal from the concentration cell.

6. A process for increasing the concentration of a first solute in one separated portion of a given solution while decreasing the concentration of said rst solute in another portion of said given solution as set forth in claim 5 in which removal of the second solute is by extraction with another solvent.

7. A process for increasing the concentration of a first solute in one separated portion of a given solution while decreasing the concentration of said rirst solute in another portion of said given solution as set forth in claim 5 in which removal of the second solute is sorption by a solid material.

8. A process for increasing the concentration of a iirst solute in one separated portion of a given solution while decreasing the concentration of said rst solute in another portion of said given solution as set forth in claim 5` in which removal of the second solute is by change in the temperature of the solution.

9. A process for increasing the concentration of an ionizable first solute in one separated portion of a given solu-tion While decreasing the concentration of said first solute in another portion of said given solution comprising the steps of treating the separated portion by adding thereto a second ionizable solute with one ion in common with the first solute to be varied to form a treated portion, alternately introducing said treated portion and an untreated portion -of said given solution into a concentration cell containing an ion exchange resin which exchanges ions of a charge opposite to Ithat of the like ions of the solutes so that each portion is removed from the cell before the other portion is passed therethrough and removing said added second ionizable solute from said treated portion to re-establish the condition of said treated po-rtion prior to said treatment except for the concentration of the ionizable first solute to be varied.

10. A process for increasing the concentration of a solute in a rst portion of a solution while decreasing the concentration of said solute in a second portion of the solution comprising the steps of introducing the rst and second portions on opposite sides of a phase divider having communicating avenues from one side to the other preventing the rapid mixing of the portions .and permeable to the solute to be varied, producing a temperature difference between said first and second portions and 1 1' 1 2 transferring the solute to be varied through the phase OTHER'REFERENCES divider and separately removing said rst and second por- Bent: Science, v01; 88 1938, pp 525 526 relied upon nous from Sald C611- Donnan: chemical Reviews, v01. 1, 1924, pp.` 73-90 relied on. References Cted by the Examiner 5 Ellis; Fresh Water From the Ocean, copyright 1954 UNITED STATES PATENTS by The Conservation Foundation, Inc.; pages 78-81 relied 2,023,109 12/*1935 van Dijck 21o-23 X #P011- 2,159,434 l; llr M23-23,11 MORRIS o. woLK, Primary Examiner. gg 7/1963 Rid "nn 21g-22 10 JOSEPH SCOVRONEK Examim 3,132,095 5/ 1964 Wolf et al. 210-23 E. G. WHITBY, Assistant Examiner. 

1. A PROCESS COMPRISING A SERIES OF TREATMENTS FOR INCREASING THE CONCENTRATION OF AN IONIZABLE FIRST SOLUTE IN ONE SEPARATED PORTION OF A GIVEN SOLUTION WHILE DECREASING THE CONCENTRATION OF SAID FIRST SOLUTE IN ANOTHER PORTION OF THE SAID GIVEN SOLUTION, COMPRISING THE STEPS OF TREATING THE SEPARATED PORTION OF THE SOLUTION BY ADDING THERETO A SECOND IONIZABLE SOLUTE WITH ONE ION COMMON TO THE FIRST SOLUTE TO BE VARIED, INTRODUCING SAID TREATED SEPARATED PORTION INTO A CONCENTRATION CELL CONTAINING AN ION EXCHANGE RESIN WHICH EXCHANGES IONS OF CHARGE OPPOSITE TO THAT OF THE LIKE IONS OF THE SOLUTES, AND EXCHANGING THE IONS HAVING CHARGES OPPOSITE TO THE LIKE IONS OF THE SOLUTES TO INCREASE THE CONCENTRATION OF THE FIRST SOLUTE IN THE TREATED SEPARATED PORTION, REMOVING THE THUS ION EXCHANGE TREATED PORTION FROM THE CELLS TO FORM THE SEPARATED FIRST TREATED PORTION ALTERNATINGLY INTRODUCING AN UNTREATED PORTION OF THE GIVEN SOLUTION TO THE CONCENTRATION CELL, EXCHANGING IONS HAVING A CHARGE OPPOSITE TO THAT OF THE LIKE IONS OF THE SOLUTES FOR DECREASING THE CONCENTRATION OF THE FIRST SOLUTE AND FOR ACQUIRING THE SECOND IONIZABLE SOLUTE TO FORM A SECOND ION EXCHANGE TREATED PORTION, REMOVING THE SECOND ION EXCHANGE TREATED PORTION FROM THE CONCENTRATION CELL TO FORM THE SEPARATED SECOND TREATED PORTION AND REMOVING THE SECOND SOLUTE FROM SAID SEPATED FIRST AND SECOND TREATED PORTION TO RE-ESTABLISH THE CONDITION OF SAID PORTIONS PRIOR TO THE ADDITION OF SAID SECOND SOLUTE EXCEPT FOR THE DEGREE OF CONCENTRATION OF THE FIRST SOLUTE TO BE VARIED. 